Japanese Patent Application Laid-open (JP-A) No. H5-254352 discloses a fuel outflow prevention device for a vehicle fuel tank having a structure where a float valve and a fuel outflow prevention valve are disposed inside a gas chamber in a fuel tank and where an evaporation passage communicated with the outflow prevention valve is opened and closed by an electromagnetic valve.
In the technology disclosed in JP-A No. H5-254352, during refueling, the electromagnetic valve is closed. Because of this, when the fuel level reaches a full level, the float valve becomes closed and the evaporation passage becomes cut off, so the gas chamber becomes tightly closed to thereby prevent overfill when the fuel tank is full.
Then, when refueling is completed, the electromagnetic valve is opened so that the fuel outflow prevention valve communicates the gas chamber to a canister, so the pressure of the gas chamber inside the fuel tank is maintained equal to or lower than a fixed pressure. Additionally, when the vehicle becomes inclined or overturns, the float valve and the fuel outflow prevention valve become closed to thereby stop fuel outflow from the fuel tank.
In the structure disclosed in JP-A No. H5-254352, a valve having a float (the float valve that regulates the full level or the fuel outflow prevention valve) is disposed in open portions (sections opening to the inside of the fuel tank) of the evaporation passages. Because of this, when the fuel is inclined, the valve having the float becomes immersed in the fuel to ensure that liquid fuel does not move from a communicating pipe to the canister.
In the structure disclosed in JP-A No. H5-254252, by ensuring that the fuel outflow prevention valve does not become immersed in the fuel inside the fuel tank even in a state in which the fuel surface is inclined, the gas in the gas chamber (gas layer) can be moved to the canister to prevent an excessive increase in the internal pressure of the fuel tank. However, the valve having the float has a predetermined height, so when the liquid level when the fuel surface is inclined is set lower than this valve, the full level also becomes set low. For this reason, the inside of the fuel tank cannot be effectively used to increase the effective capacity of the fuel tank (the amount of fuel that the fuel tank can hold).
In consideration of the circumstances described above, an object of the present disclosure is to make it possible for the gas to move from the fuel tank to the canister when the fuel surface in the fuel tank is inclined and to ensure a large effective capacity for the fuel tank.